Preparation And Characterization Of ZnS/Fe₃O₄Nanocomposites

In this paper, Fe3O4nanoparticles, ZnS quantum dots and ZnS/Fe3O4nanocomposites doped with ZnS quantum dots were synthesized respectively through chemical co-precipitation method. The X-ray diffractormeter was adopted to investigate the crystal structure of the products. The size and morphology of the products were observed by transmission electron microscope (TEM) and high resolution transmission electron microscope (HR-TEM). The photoluminescence and ultraviolet absorption spectrum were used to probe the optical properties of the products. The magnetism of the products was characterized by vibrating sample magnetometor (VSM). The whole research proceeded in three different phrases:1. Fe3O4nanoparticles were prepared by chemical co-precipitation method. The dispersive ability of the nanoparticles was investigated by three different dispersants (Span-80, Tween-80, PEG-2000). The results show that PEG-2000has the more positive effect on improving the nanoparticles dispersive ability than the other two kinds of dispersants. The crystal structure of the products was tested by XRD. The results indicate that the as-synthesized Fe3O4belong to category of inverse spinel type structure of Fe3O4. The size distribution and morphology of the products were observed by TEM and HR-TEM. The results demonstrate that small distribution Fe3O4nanoparticles can be obtained by this chemical co-precipitation method with PEG-2000as dispersant. Magnetic property of the products was characterized by VSM. The results show that the as-synthesized Fe3O4particles possess superparamagnetism, and the saturation magnetization of the product is lower than bulk Fe3O4materials.2. The chemical co-precipitation method was used to synthesize ZnS quantum dots. Three different emulsifiers were used to investigate the dispersive effect on ZnS quantum dots. The results show that the dispersive ability of the ZnS can be enhanced greatly with PEG-2000as the dispersant. The results of XRD analysis of ZnS indicate that the crystal structure of the samples is the structure of blende and the average size is about4.6nm which was estimated by Sherra’s formula. The ultraviolet absorption property of the as-synthesized ZnS quantum dots was studied by ultraviolet absorption spectrum. The results show that the ultraviolet absorption of the products has evident blue shift compared with bulk ZnS materials, which indicates the successfully synthesis of the ZnS quantum dots. The products present strong blue light emission at wavelength of450nm when investigated by photoluminescence spectrum.3. A two-step chemical co-precipitation method was developed based on the chemical co-precipitation method. With this kind method, ZnS/Fe3O4nanocomposites doped with ZnS quantum dots were prepared. The optical and magnetism properties were tested. The results of the optical examination show that the as synthesized ZnS/Fe3O4nanocomposites have the ability of photoluminescence and the intensity of the photoluminescence varied when the ZnS quantum dots content changed. The composites present superparamagnetism when characterized by VSM, and the saturation magnetization of the products changed with different content of ZnS doped in the composites. Bi-function of ZnS/Fe3O4nanocomposites with fluorescence and superparamagnetism which the intensity of fluorescence and saturation magnetization is tunable can be obtained through varying the concentration ratio between ZnS and Fe3O4.